1. Field of the Invention
Some embodiments of the invention are systems and methods for characterizing a display using a camera device (e.g., a handheld or other mobile camera device) to measure light emitted by the display, and optionally also to calibrate the display using control parameters determined using measurements of the light by the camera device.
2. Background of the Invention
Throughout this disclosure including in the claims, the expression performing an operation “on” signals or data (e.g., filtering the signals or data) is used in a broad sense to denote performing the operation directly on the signals or data, or on processed versions of the signals or data (e.g., on versions of the signals that have undergone preliminary filtering prior to performance of the operation thereon).
Throughout this disclosure including in the claims, the expression “system” is used in a broad sense to denote a device, system, or subsystem. For example, a subsystem that implements a filter may be referred to as a filter system, and a system including such a subsystem (e.g., a system that generates X output signals in response to multiple inputs, in which the subsystem generates M of the inputs and the other X-M inputs are received from an external source) may also be referred to as a filter system.
Throughout this disclosure including in the claims, the noun “display” and the expression “display device” are used as synonyms to denote any device or system operable to display an image or to display video in response to an input signal. Examples of displays are computer monitors, television sets, and home entertainment system monitors or projectors.
Throughout this disclosure including in the claims, the terms “calibration” and “recalibration” of a display denote adjusting at least one parameter or characteristic of the display, e.g., color, brightness, contrast, and/or dynamic range characteristics of the display. For example, calibration of a display device can be implemented by performing preprocessing or other processing on input image data (to be displayed by the display device) to cause the light emitted by the display device in response to the preprocessed (or otherwise processed) image data (typically after further processing is performed thereon) to have one or more predetermined color, brightness, contrast, and/or dynamic range characteristics. In accordance with some embodiments of the invention, calibration is performed “automatically” in the sense that it is performed without human user intervention.
Throughout this disclosure including in the claims, the term “processor” is used in a broad sense to denote a system or device programmable or otherwise configurable (e.g., with software or firmware) to perform operations on data (e.g., video or other image data). Examples of processors include a field-programmable gate array (or other configurable integrated circuit or chip set), a digital signal processor programmed and/or otherwise configured to perform pipelined processing on video or other image data, a programmable general purpose processor or computer, and a programmable microprocessor chip or chip set.
Throughout this disclosure including in the claims, measured “light intensity” is used in a broad sense, and can denote measured luminance or another measured indication of light intensity appropriate in the context in which the expression is used.
Throughout this disclosure including in the claims, the term “camera” is used in a broad sense to denote a light sensor (e.g., a colorimeter or other sensor whose output can be analyzed to determine a color or frequency spectrum of sensed light), or a camera including an image sensor array (e.g., a CCD camera), or a camera of any other type. Typical embodiments of the invention employ a mobile device which includes a camera operable to sense an image displayed by a monitor or other display and to output data indicative of the sensed image (or one or more pixels thereof).
Throughout this disclosure including in the claims, the expression “mobile device” denotes a device which is readily portable by a human user. An example of a mobile device is a handheld device, which is configured to be held in a human user's hand during use and is typically carried by a human user between uses.
Throughout this disclosure including in the claims, the expression “camera device” denotes a device which includes (e.g., is) a camera and a processor coupled to receive the camera's output, and which is operable to measure at least one characteristic of light emitted by a display device (e.g., while the display device displays at least one test image). For example, a mobile phone which includes a camera and a processor coupled to receive the camera's output may be a camera device as defined in this paragraph. Typical embodiments of the invention include or employ a camera device which is a mobile device.
Throughout this disclosure including in the claims, the expression “uncalibrated camera device” denotes a camera device which includes (e.g., is) a camera and a processor coupled to receive the camera's output, and which is operable to measure at least one characteristic of light emitted by a display device (e.g., while the display device displays at least one test image) in a manner emulating measurement of the same light by a reference camera having known sensitivity function but without preknowledge of the sensitivity function of the camera device's camera. Some embodiments of the invention include or employ an uncalibrated camera device which is a mobile device (e.g., a handheld device). Some other embodiments of the invention include or employ an uncalibrated camera device which is not readily portable. In some embodiments, an uncalibrated camera device (e.g., implemented as a mobile device) is operable to download data indicative of a prior characterization or calibration of a display (e.g., data indicative of a sensitivity function of a reference camera employed to perform the prior characterization or calibration) and to measure at least one characteristic of light emitted by the display using the camera device's camera and the downloaded data in connection with a recalibration of the display.
It is conventional for a user to manually adjust controls of a display device to adjust or calibrate the device while the device displays test patterns (e.g., in response to test pattern data read from a DVD or other disk). While a display device displays test patterns, it is also conventional to use a colorimeter or camera to generate data that characterize the display device and/or are indicative of recommended settings for adjusting or calibrating the display device (e.g., to match target settings). With knowledge of such data, a user can manually adjust (or manually enter commands which cause adjustment of) controls of the display device to obtain a visually pleasing and/or acceptable displayed image appearance or to match target settings. It is also conventional to program a processor to generate control values in response to such data and to assert the control values to a graphics card of the display device to calibrate the display device. For example, it is known to use a computer programmed with appropriate software to generate control values which determine look-up tables (LUTs) in response to such data and to assert the control values to the graphics card (e.g., to match target settings previously provided to the computer).
During adjustment of display devices, test patterns are often displayed. For example, commercially available disks (e.g. DVDs) that store test patterns can be played to cause the device being adjusted to display a sequence of test patterns and prompts to the viewer to manually adjust relevant controls of the device while viewing the patterns (e.g., to correct the device's video parameters to optimize video display).
The adjustment of a video display for optimal picture quality, and the general assessment of displayed image quality and display device characteristics is a challenging task, generally thought to be well outside an average consumer's capabilities. It would be desirable to implement methods and systems that allow consumers to achieve correct display characterization and calibration with acceptable cost and effort. Typical embodiments of the present invention are display calibration methods and systems that employ a mobile (e.g., networked) camera device to perform display calibration, and/or to provide display assessment and education to consumers in a user friendly way.